LibriVox

Similar to Project Gutenberg, LibriVox is an online digital library of free public domains books, but in audio format. Read entirely by volunteers, LibriVox by had a catalogue of over 6,244 unabridged books available to download by the of 2012. And every month, the project is adding on average 89 audiobooks per month. Besides downloading the site, you can also obtain these audiobooks directly through your smartphones via free apps like Audiobooks.